Drug Monograph on Rifampicin - page 5
Keywords: rifampicin, drug monograph, pharmacology, efficay, therapeutic uses, pharmacodynamics, Prophylaxis of meningococcal meningitis rifampin rifadin SA infections tuberculosis essay on rifampicin pharmacokinetics absorption distribution matabolism excretion bmj referecing
By Einstein10 on 30/12/2009
Level: Foundation Degree
Page Number: 5 of 11 pages: 1 2 3 4 5 6 7 8 9 10 11Over 100 million media files online, search for anything you want! No time limits, no per download fees, no bandwith or content limits.
CheapCarSearch.com - As seen on TV!
Thousands of cars become government & bank property every day through seizures and surplus laws. The constant exchange of vehicles and the enormous expense to store them, means amazing deals and guaranteed rock bottom prices for you! As Much as 80% OFF!
Saturable absorption of Rifampicin could have a link to its poor intestinal absorption. 23 A recent study showed that permeation of Rifampicin absorption was significantly higher from the serosal to the mucosal side of secretion compared to the mucosa-serosal side of the jejunum and ileum as shown in figure 1. The absorption through the duodenum increased by 300 μg/mL, as shown in Figure 2 indicating the existence of saturable absorption. Therefore, this study shows that efflux-permeation absorption in the jejunum and saturable absorption mechanism of Rifampicin in the intestine, act as a barrier to the absorption of the drug. 23
Distribution
Despite Rifampicin use for over 40 years. Little is known about its distribution in human lung tissue. 24
Table 5- 24 Pharmokinetic Properties of Rifampicin
Solubility Lipid>>>Water
Absorption from GI Tract Almost Complete
Protein Binding (%) 85
Apparent volume of distribution (% body Weight) 160
Tissue Concentration Intracellular
Half-Life Min 200-uninduced
120-Induced
Metabolism 30-60% by deacetylated but active 10-20% Oxidised and inactive
Rifampicin uses plasma proteins to distribute itself and is approximately 85% protein bound. 22 Approximately 30%, of the 80% which is bound is specifically bound to albumin where it may compete with other drugs e.g. warfarin 23
Rifampicin as a whole is lipid soluble with only 25% of the drug ionized at physiological pH therefore it readily diffuses into tissues and bodily fluids including the cerebrospinal fluid, where the levels of rifampicin are approximately one-tenth of what is present in the blood 25.
The volume of distribution is approximately 11.kg-1. 25
Distribution in Tuberculosis Meningitis Patients
Table 6- 26 RIF was administered in a single dose of 600 mg to fasting healthy individuals and to fasting patients suffering from active tuberculosis meningitis
After 3 Hours After 6 Hours After 9 Hours After 12 Hours After 24 Hours
CSF Concentration (mcg/ml) 0.03 0.23 0.81 0.3 0.13
Patients’ with tuberculosis meningitis (mcg/ml) 1.75 2.38 1.43 0.85 0.06
Results from the table show that the distribution of Rifampicin crosses the Blood-Brain Barrier as we see the concentration of Rifampicin in the Cerebral Spinal Fluid increasing from 0.03-0.81 mcg/ml between 3-9 hours. Also it can be concluded that Rifampicin moves more freely in patients infected with tuberculosis meningitis compared to patients without the disease. The exact mechanism is unknown. 26
Metabolism
The metabolism of rifampicin is carried out in the liver by hydrolysis and dasacylation and yields 2 metabolites, 25-O-deacetyle rifampicin and 3-Formylrifampicin.28
Deacylation at the C-25 position results in a more polar compound. According to the dose administered the amount of rifampicin which may be excreted into the bile will vary between one third to one eighth of the total dose.
Last 5 comments…
There have been no comments posted for this article, but you need to register if you want to be the first!